Technical Field
The present disclosure relates to a light-emitting device, more particularly, to a light-emitting device with improved brightness.
Description of the Related Art
The light-emitting diodes (LEDs) of the solid-state lighting elements have the characteristics of low power consumption, low heat generation, long operation life, crash proof, small volume, quick response and good opto-electrical property like light emission with a stable wavelength, so the LEDs have been widely used in household appliances, indicator light of instruments, and opto-electrical products, etc. As the opto-electrical technology develops, the solid-state lighting elements have great progress in the light efficiency, operation life and the brightness, and LEDs are expected to become the main stream of the lighting devices in the near future.
A conventional LED basically includes a substrate, an n-type semiconductor layer, an active layer and a p-type semiconductor layer formed on the substrate, and p/n electrodes respectively formed on the p-type/n-type semiconductor layers. When imposing a certain level of forward voltage to the LED via the electrodes, holes from the p-type semiconductor layer and electrons from the n-type semiconductor layer are combined in the active layer to release light. However, the electrodes shelter light emitted from the active layer, and current may be crowded in semiconductor layers near the electrodes. Thus, an optimized electrode structure is needed for improving brightness, optical field uniformity and lowering an operating voltage of the LED.
Besides, the conventional LED has a quadrangular shape. The substrate has sidewalls forming four 90° interior angles. An internal reflection of light inside the quadrangular LED may easily occur due to this kind of LED shape so that the light may hardly escape from the LED. As a result, light extraction and brightness of the LED deteriorate.